A. Field of the Invention
This invention relates to a process for treating aldol-condensation polyol waste liquor.
B. Description of the Prior Art
It is well known that aldol-condensation polyol waste liquors contain sodium formate, polyol, water and organic by-products. Generally, this waste liquor is disposed of. However, due to ecological reasons, disposing of such waste liquors can be a problem. Robeson, U.S. Pat. No. 3,357,899 of Dec. 12, 1967, has proposed a process for treating such waste liquor involving acidifying to convert the sodium formate to sodium sulfate and formic acid. The sodium sulfate is removed as a solid, and the formic acid is removed as an azeotrope with water. The polyol is not recoverable in Robeson's process since it is contaminated with formic acid, and the formic acid is only recoverable in the form of an azeotrope. Thus Robeson's process is uneconomical and impracticable.
Other methods of treating aldol-condensation waste liquors are disclosed by Leonard, U.S. Pat. No. 3,179,704, involving extraction with dimethyl formamide; Snow et al, U.S. Pat. No. 2,441,602 involving extraction of the organics with ethanol; Clunie et al., U.S. Pat. No. 3,066,171, involving ozone treatment; and McGrath, U.S. Pat. No. 2,690,993, involving azeotropic distillation with water. All of these processes suffer from one or more disadvantage as compared with the process of the invention.
A need exists for an economical and practical process which results in recoverable, separated products which have sufficient value to counter-balance the waste liquor treatment costs.